ABBA Relay

Using a track or a made up loop, divide the runners into evenly matched pairs. Runner A starts and runs a lap steadily, on completing the lap runner B joins in and they race a lap. A drops out and B runs steady for a lap. B stops, A runs steady for a lap, then races B for a lap, and so on.

So A, AB, B, A, AB, B, A, AB …

An alternative is to do A, AB, B, BA, A, AB, B, AB, A, AB, B …

In this case they are running 3 laps without a break and racing two of these. I haven’t tried this, but suspect it might be much harder.